i'm tempted to nominate the opening to Star Trek 2009.
its maybe not the best ever (i would have to spend a much longer time thinking about a hell of a lot of films) but it really grabs you by the seat of the pants in a way i haven't felt in a very long time, tosses you around and doesn't let go til its finished with you.
i think that opening is practically the backbone of the reboot.
it made everyone in the theatre sit up and pay attention to what followed.
i pretty much got my quite solidly "not interested in Star Trek" brother to watch the entire film by saying "just watch the opening..."
...although this was a little underhand on my part as he has a young toddler so as soon as the pregnancy aspect came in i knew he was gonna pay at least some attention due to recently becoming a dad
by the end of the opening sequence he was pretty much welling up
in fact i think i'll go watch it now